The present invention relates to a radio signal processing device and a semiconductor device, and a radio signal processing device and a semiconductor device including, for example, an oscillator configured so that the oscillation frequency thereof can vary.
Further, the present invention relates to an oscillation frequency variation correction method, and an oscillation frequency variation correction method by which, for example, the variation of the oscillation frequency of the oscillator is corrected.
As an example of related techniques, Japanese Unexamined Patent Application Publication No. Hei 11 (1999)-308285 discloses a direct modulation FSK (Frequency Shift Keying) transmitter for MCA (Multi-Channel Access). The direct modulation FSK transmitter for MCA described in Japanese Unexamined Patent Application Publication No. Hei 11 (1999)-308285 has a phase locked loop (PLL), a voltage controlled oscillator (VCO), and a transmission power amplifier. In Japanese Unexamined Patent Application Publication No. Hei 11 (1999)-308285, the voltage controlled oscillator is controlled so as to allow the phase locked loop to output an oscillation signal having a target frequency for a specific channel.
In the direct modulation FSK transmitter for MCA described in Japanese Unexamined Patent Application Publication No. Hei 11 (1999)-308285, if the electric power supplied to the transmission power amplifier is turned on when radio transmission is started, the input impedance of the transmission power amplifier is changed, and the oscillation frequency of the voltage controlled oscillator arranged in the previous stage of the transmission power amplifier is changed due to a change in the input impedance. Japanese Unexamined Patent Application Publication No. Hei 11 (1999)-308285 describes that in order to suppress the variation of the oscillation frequency when starting the supply of the electric power to the transmission power amplifier, a control signal for turning on or off the transmission power amplifier is added to the voltage controlled oscillator to cancel the variation of the oscillation frequency.
Further, as another example of related techniques, Japanese Patent No. 5668082 discloses an RFIC (Radio Frequency Integrated Circuit) for communications. The RFIC described in Japanese Patent No. 5668082 has a PLL circuit including an LC oscillator. Japanese Patent No. 5668082 describes that in the case where an amplifier in the transmission output stage is switched to on or off, the voltage of a power supply line varies, and the PLL circuit may be unlocked due to the variation of the voltage. In order to solve the problem of the unlocking in Japanese Patent No. 5668082, the capacitance value of the LC oscillator is controlled in accordance with a control signal supplied to the amplifier causing noise. Thereby, the variation of the oscillation frequency due to a change in the state of the amplifier can be suppressed.